Research Article |
Corresponding author: Werner Klotz ( wklotz@aon.at ) Academic editor: Ingo S. Wehrtmann
© 2021 Werner Klotz, Thomas von Rintelen, Daisy Wowor, Chris Lukhaup, Kristina von Rintelen.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Klotz W, von Rintelen T, Wowor D, Lukhaup C, von Rintelen K (2021) Lake Poso's shrimp fauna revisited: the description of five new species of the genus Caridina (Crustacea, Decapoda, Atyidae) more than doubles the number of endemic lacustrine species. ZooKeys 1009: 81-122. https://doi.org/10.3897/zookeys.1009.54303
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Lake Poso, an ancient lake system on the Indonesian island Sulawesi, harbours an endemic species flock of six, four lacustrine and two riverine species of the freshwater shrimp genus Caridina. In this study, five new lacustrine species are described, bringing the total to eleven species altogether. The number of lacustrine species is more than doubled to nine species compared to the last taxonomic revision in 2009. One of them, Caridina mayamareenae Klotz, Wowor & von Rintelen, sp. nov., even represents the first case of an atyid shrimp associated with freshwater snails which is morphologically adapted to living in shells. An integrative approach was used by providing a combination of morphological, ecological, and molecular data. Based on standard morphological characters, distribution, substrate preferences, and colouration of living specimens in the field, five distinct undescribed species could be distinguished. To support our species-hypothesis based on the mitochondrial genes 16S and COI, a molecular phylogeny was used for all eleven species from Lake Poso. All species form a well-supported monophyletic group, but only four morphospecies consistently correspond to mtDNA clades – a possible reason could be introgressive hybridisation, incomplete lineage sorting, or not yet fixed species boundaries. These results are discussed further in the context of adaptive radiation, which turned out to be more diverse than previously described. Finally, yet importantly, subjecting all new species to similar threats and to the same IUCN category and criterion than the previously described species from the lake is recommended.
Adaptive radiation, ancient lake, freshwater biodiversity, Indonesia, integrative taxonomy, Sulawesi
Lake Poso (Fig.
The endemic species flock of atyid freshwater shrimps of the genus Caridina in Lake Poso was first studied by
Here, we use an integrative taxonomic approach to study newly collected material from Lake Poso to a) discover new, so far unknown species from the lake, b) provide a combination of morphological, ecological, and molecular data to describe the newly discovered species, c) provide two different identification keys (a regular key for preserved specimens and a key for pre-sorting living specimens in the field without having to use a microscope), and d) discuss the results in context of adaptive radiation and conservation status of the previously revised Lake Poso species flock.
Specimens were caught by hand net and preserved in 75–95% ethanol during several fieldtrips to Lake Poso (Fig.
All material examined is deposited in Museum Zoologicum Bogoriense, Cibinong, Indonesia (
DNA was extracted from abdominal tissue using either a Qiagen Blood and Tissue Kit or a Qiagen BioSprint with the Plant Kit (but lysis with 10ml Qiagen Proteinase K (20mg/ml) added) according to the manufacturer's instructions. Fragments of the mitochondrial 16S rRNA (16S, ~ 590 bp) and cytochrome oxidase subunit I (COI, 861 bp) genes were amplified by polymerase chain reaction (PCR) and sequenced using primers 16S-F-Car and 16S-R-Car1 (16S), and COI-F-Car and COI-R-Car (COI) (
Contigs of forward and reverse strands were assembled using Geneious Prime (v. 2019.2.1) and corrected by eye. Sequences were aligned by eye (COI) and with MAFFT (16S) (
All new sequences (51 from Lake Poso species, 1 outgroup taxon) have been deposited in GenBank (for accession numbers and museum voucher numbers see Suppl. material
Phylogenetic trees were reconstructed by Bayesian inference (BI;
We distinguished five morphologically distinct and undescribed species that could be separated clearly based on the examination of living specimens in the field (Figs
Living specimens of Caridina spp in Lake Poso 1. A Caridina schenkeli von Rintelen & Cai, 2009 B C. acutirostris Schenkel, 1902 C C. caerulea von Rintelen & Cai, 2009 D C. ensifera Schenkel, 1902 E C. mayamareenae sp. nov. male F, G C. longidigita Cai & Wowor, 2007 H C. sarasinorum Schenkel, 1902. Not to scale. Photo: C. Lukhaup (A, C), W. Klotz (B, D–H).
Living specimens of Caridina spp in Lake Poso 2. A, B Caridina mayamareenae sp. nov. C C. lilianae sp. nov. D Two snail species Celetaia persculpta and Tylomelania sp. on soft substrate. Empty shells of these species are shelter for C. mayamareenae sp. nov. E, F C. poso sp. nov. G C. marlenae sp. nov. H C. fusca sp. nov. Not to scale. All photographs: W. Klotz.
Current checklist of endemic species of the genus Caridina from Lake Poso, Indonesia.
Species | Remarks | Reference |
---|---|---|
Caridina acutirostris Schenkel, 1902 | Exclusively riverine species, endemic to Lake Poso catchment |
|
C. caerulea von Rintelen & Cai, 2009 | Endemic to Lake Poso (excluding rivers) |
|
C. ensifera Schenkel, 1902 | Endemic to Lake Poso (excluding rivers) |
|
C. fusca Klotz, Wowor & von Rintelen, sp. nov. | Endemic to Lake Poso (excluding rivers) | This study |
C. lilianae Klotz, Wowor & von Rintelen, sp. nov. | Endemic to Lake Poso (excluding rivers) | This study |
C. longidigita Cai & Wowor, 2007 | Endemic to Lake Poso (excluding rivers) |
|
C. marlenae Klotz, Wowor & von Rintelen, sp. nov. | Endemic to Lake Poso (excluding rivers) | This study |
C. mayamareenae Klotz, Wowor & von Rintelen, sp. nov. | Endemic to Lake Poso (excluding rivers); hiding in empty snail shells | This study |
C. poso Klotz, Wowor & von Rintelen, sp. nov. | Endemic to Lake Poso (excluding rivers) | This study |
C. sarasinorum Schenkel, 1902 | Endemic to Lake Poso (excluding rivers) |
|
C. schenkeli von Rintelen & Cai, 2009 | Exclusively riverine species, endemic to Lake Poso catchment |
|
1 | Tip of rostrum reaching end to distinctly overreaching end of scaphocerite (Fig. |
2 |
– | Tip of rostrum not reaching end of scaphocerite (Fig. |
8 |
2 | Tip of rostrum reaching or slightly overreaching end of scaphocerite (Fig. |
3 |
– | Tip of rostrum reaching distinctly beyond end of scaphocerite (Fig. |
4 |
3 | Epipods present on first and second pereiopods (Fig. |
C. schenkeli von Rintelen & Cai, 2009 |
– | Epipod absent from all pereiopods (Fig. |
C. marlenae sp. nov. |
4 | Tip of rostrum reaching beyond end of scaphocerite, ~ 0.9–1.4 times as long as carapace, long but not very slender (Fig. |
5 |
– | Tip of rostrum reaching far beyond end of scaphocerite, ~ 1.4–2.8 times as long as carapace, long and quite slender (Fig. |
6 |
5 | Epipod present on first pereiopod; chelae of first and second pereiopods stout, setae on tip of fingers ~ half as long as chelae (Fig. |
C. sarasinorum Schenkel, 1902 |
– | Epipod absent from all pereiopods; chelae of first and second pereiopods very slender, setae on tip of fingers ~ as long as chelae (Fig. |
C. longidigita Cai & Wowor, 2007 |
6 | Epipod absent from all pereiopods, vestigial epipod present on third maxilliped (Fig. |
C. poso sp. nov. |
– | Epipods present on third maxilliped, first and second pereiopods (Fig. |
7 |
7 | Rostrum 1.4–2.3 times as long as carapace, with distinctly less teeth (dorsal 9–15, ventral 16–29) (Fig. |
C. ensifera Schenkel, 1902 |
– | Rostrum 1.9–2.6 times as long as carapace, with distinctly more teeth (dorsal 11–20, ventral 26–48) (Fig. |
C. caerulea von Rintelen & Cai, 2009 |
8 | Rostrum very short, tip not reaching distal margin of eye (Fig. |
C. lilianae sp. nov. |
– | Rostrum moderately short, tip distinctly overreaching distal margin of eye | 9 |
9 | Tip of rostrum reaching end of third segment of antennular peduncle (Fig. |
C. fusca sp. nov. |
– | Tip of rostrum reaching end of second segment of antennular peduncle (Fig. |
10 |
10 | Rostrum high, maximum depth of rostrum more than maximum dorsoventral diameter of eye, ~ 0.17 of dorsal margin of rostrum distal without tooth (Fig. |
C. mayamareenae sp. nov. |
– | Rostrum slender, maximum depth of rostrum less than maximum dorsoventral diameter of eye, ~ 0.3–0.5 of dorsal margin of rostrum distal without tooth (Fig. |
C. acutirostris Schenkel, 1902 |
Morphological characters used in the identification keys A tip of rostrum distinctly overreaching end of scaphocerite B tip of rostrum not reaching end of scaphocerite C tip of rostrum reaching end of scaphocerite D epipods present on third maxilliped and first and second pereiopods E epipod present on third maxilliped but absent from all pereiopods F rostrum long but not very slender G chelae of first and second pereiopods stout, setae on tip of fingers approx. half as long as chelae H chelae of first and second pereiopods very slender, setae on tip of fingers approx. as long as chelae I epipod vestigial present on third maxilliped and absent from all pereiopods J rostrum of C. ensifera Schenkel, 1902 K rostrum of C. caerulea von Rintelen & Cai, 2009 L rostrum reaching end of second segment of antennular peduncle and slender.
1 | Shrimps collected from the rivers | 2 |
– | Shrimps collected from the lake | 3 |
2 | Rostrum approximately as long (0.9–1.1 times) as carapace; body transparently yellowish or brownish (Fig. |
C. schenkeli von Rintelen & Cai, 2009 |
– | Rostrum always distinctly shorter (0.3–0.7 times) than carapace; body transparently yellowish or brownish (Fig. |
C. acutirostris Schenkel, 1902 |
3 | Rostrum distinctly long and very slender, bent upwards, tip reaching far beyond end of scaphocerite; body rather slender and mainly transparent or with mottled pattern | 4 |
– | Rostrum short to moderately long and not conspicuously slender, tip slightly reaching beyond end of scaphocerite or shorter; body usually more robust and less transparent | 6 |
4 | Body showing a clearly visible red-and-white stripe pattern (Fig. |
C. poso sp. nov. |
– | Body rather yellowish-transparent without stripe pattern; tail fan with colour marks | 5 |
5 | Legs and rostrum bluish; tail fan with two conspicuous blue patches (Fig. |
C. caerulea von Rintelen & Cai, 2009 |
– | Legs and rostrum yellowish-reddish; tail fan with two conspicuous red patches (Fig. |
C. ensifera Schenkel, 1902 |
6 | Rostrum conspicuously high; large females whitish, frequently with broad red stripes and blotches, eggs green (Fig. |
C. mayamareenae sp. nov. |
– | Rostrum not conspicuously high; usually not found in empty snail shells | 7 |
7 | Rostrum very short, tip not reaching distal margin of eyes and body transparent-whitish (Fig. |
C. lilianae sp. nov. |
– | Rostrum distinctly longer, clearly overreaching distal margin of eyes; lives on various types of substrates | 8 |
8 | Chelae on first two pairs of pereiopods with very long and clearly visible fingers, setae on tip of fingers as long as or longer than chelae (Fig. |
C. longidigita Cai & Wowor, 2007 |
– | Chelae on first two pairs of pereiopods not conspicuously long with rather short fingers, setae on tip of fingers shorter than chelae (Fig. |
9 |
9 | Body bright reddish with large white dots (Fig. |
C. marlenae sp. nov. |
– | Body dark reddish or brown with well-defined white transversal bands | 10 |
10 | Body dark reddish or brown with sharply defined white transversal bands on first, third, fifth and sixth abdominal segments (Fig. |
C. fusca sp. nov. |
– | Body with a similar colouration and pattern, but bands less well-defined and scraggy (Fig. |
C. sarasinorum Schenkel, 1902 |
Caridina H. Milne Edwards, 1837
Holotype: ov. ♀ cl. 2.9 mm (
Cephalothorax and cephalic appendages. Postorbital carapace length 2.4–2.8 mm (n = 10). Rostrum (Fig.
Caridina fusca sp. nov. Morphology 1. Paratype ov. ♀, cl. 2.7 mm,
Abdominal somites, telson, and uropods. Sixth abdominal somite 0.54–0.58 (median 0.56, n = 4) times carapace length, 1.53–2.21 (median 1.77, n = 4) times as long as fifth somite, 0.94–1.00 (median 0.98, n = 4) times as long as telson. Distal margin of telson (Fig.
Mouthparts and branchiae. Incisor process of mandible (Fig.
Pereiopods. Chelae of first and second pereiopods (Fig.
Caridina fusca sp. nov. Morphology 2. Paratype ov. ♀, cl. 2.7 mm,
Pleopods. Appendix masculina (Fig.
Body dark reddish or brown with tiny light bluish dots, well-defined white transversal bands on the first, third, fifth, and sixth abdominal segments (Fig.
Ovigerous females with few eggs (35, n = 1). Size of eggs 0.77–0.81 × 0.44–0.49 mm (n = 3).
The Latin word fuscus refers to the species’ dark reddish or brown colouration (Fig.
Caridina fusca sp. nov. is endemic to Lake Poso. Specimens were found at two localities within the lake, in a small bay south of the town of Tentena at the east shore and in a bay at the west shore.
Caridina fusca sp. nov. is found under rocks in deep water (more than 5 m depth), while the morphologically similar species C. sarasinorum is usually found on various kinds of substrate like deposits of leaf litter, on wood or macrophytes (
In life colouration, C. fusca sp. nov. might be confused with C. sarasinorum, also endemic to Lake Poso. In the latter, the transversal bands on the abdomen are less defined and scraggy compared to the sharply defined straight bands in C. fusca sp. nov. In preserved condition C. fusca sp. nov. can be differentiated from C. sarasinorum by the rostrum reaching to the end of the antennular peduncle, the dorsal and ventral margin armed throughout almost to the tip vs. reaching to the distal margin of the scaphocerite or beyond, unarmed in anterior one-third to half of the dorsal margin in C. sarasinorum. Epipods are reduced on the third maxilliped and absent on all pereiopods of C. fusca sp. nov. vs. well-developed on the third maxilliped and first pereiopod, absent on second to fifth pereiopods in C. sarasinorum. The chelae of the first pair of pereiopods are not inflated, 2.29–2.73 times as long as wide, 1.17–1.34 times as long as the carpus in C. fusca sp. nov. vs. slightly inflated, 1.74–2.10 times as long as wide, 1.35–1.48 times as long as the carpus in C. sarasinorum. The carpi of the first pair of pereiopods are more slender (2.33–4.00 times as long as wide) and hardly excavated distally vs. more stout (1.75–2.22 times as long as wide) and slightly excavated distally in C. sarasinorum.
Holotype: ov. ♀ cl. 3.1 mm (
Cephalothorax and cephalic appendages. Postorbital carapace length 1.7–3.1 mm (n = 33). Rostrum (Fig.
Caridina lilianae sp. nov. Morphology 1. Paratype ov. ♀, cl. 3.1 mm,
Abdominal somites, telson and uropods. Sixth abdominal somite 0.68–0.88 (median 0.77, n = 6) times carapace length, 1.78–2.26 (median 2.00, n = 6) times as long as fifth somite, 1.08–1.29 (median 1.22, n = 6) times as long as telson. Telson (Fig.
Mouthparts and branchiae. Incisor process of mandible (Fig.
Pereiopods. Chelae of first and second pereiopods (Fig.
Caridina lilianae sp. nov. Morphology 2. Paratype ov. ♀, cl. 3.1 mm,
Pleopods. Endopod of male first pleopod (Fig.
Body colouration transparent to whitish with minute sand-coloured dots (Fig.
Ovigerous females with few eggs (35, n = 1). Size of undeveloped eggs (early stage embryos without eyespot) 0.61–0.72 × 0.37–0.39 mm, size of developed eggs (late stage embryos with eyes) 0.70–0.76 × 0.39–0.44 mm (n = 6).
Named after the second and last authors’ first daughter who is very interested in field work and helped to observe and document this species while visiting the lake in 2019.
Caridina lilianae sp. nov. is endemic to Lake Poso. Specimens were found at three localities within the lake, two within a bay south of the town of Tentena at the east shore and one in a bay at the west shore.
Caridina lilianae sp. nov. lives on very fine sand or silt (soft substrate) in shallow water (1.5–2.5m).
With its small size and the less developed chelae with scarce setae at the tip of the fingers, C. lilianae sp. nov. is similar to C. mayamareenae sp. nov. but can easily be distinguished from this species by the very short, convex rostrum (vs. rostrum conspicuous high, reaching to end of second segment of antennular peduncle or slightly overreaching this segment) and the slender third pair of pereiopods bearing long stiff setae on merus and ischium but without any spiniform setae on flexor margin (vs. third pereiopod very robust, without long simple setae on merus and ischium and dactylus with five or six spiniform setae on flexor margin). These characters also distinguish C. lilianae sp. nov. from all other Caridina spp. known from the Lake Poso. Although C. lilianae sp. nov. and C. mayamareenae sp. nov. occur in sympatry in the lake, the microhabitats of these species are quite different. Caridina mayamareenae sp. nov. lives in empty shells of aquatic snails while C. lilianae sp. nov. on soft substrate. The long stiff simple setae attached to the posterior segments of the chelipeds and pereiopods could be interpreted as a morphological adaption to this kind of habitat by preventing them to subside into the soft substrate. This hypothesis would need to be tested, though. In the field, the whitish or cream-coloured body colouration is indiscernible on light-coloured sandy habitats (Fig.
Holotype
: ♀ cl. 2.8 mm (
Caridina sarasinorum Schenkel, 1902, 1 ov. ♀ cl. 3.0 mm, 1 ♂ cl. 2.6 mm (
Cephalothorax and cephalic appendages. Postorbital carapace length 1.44–3.07 mm (n = 19). Rostrum (Fig.
Caridina marlenae sp. nov. Morphology 1. Paratype ♂, cl. 2.2 mm,
Abdominal somites, telson and uropods. Sixth abdominal somite 0.55–0.64 (median 0.62, n = 5) times carapace length, 1.93–2.23 (median 2.15, n = 5) times as long as fifth somite, 1.00–1.13 (median 1.12, n = 4) times as long as telson. Distal margin of telson (Fig.
Mouthparts and branchiae. Incisor process of mandible (Fig.
Pereiopods. Chelae of first and second pereiopod (Fig.
Caridina marlenae sp. nov. Morphology 2. Paratype ♂, cl. 2.2 mm,
Pleopods. Endopod of male first pleopod (Fig.
Body colouration bright reddish with large white dots (Fig.
Ovigerous females with few eggs (9, n = 1). Size of eggs 0.81–0.83 × 0.48–0.0.51 mm (n = 2).
Named after the second and last authors’ second daughter who is very interested in field work and helped to observe and document this species while visiting the lake in 2019.
Caridina marlenae sp. nov. is endemic to Lake Poso. Specimens were found only at one locality in a bay south of the town of Tentena at the east shore of the lake.
Caridina marlenae sp. nov. is found under rocks in deep water (more than 5 m).
With its long rostrum, approximately anterior 0.4 unarmed, C. marlenae sp. nov. is similar to C. sarasinorum, C. schenkeli and C. longidigita, all endemic to Lake Poso. In the field, body colouration alone is sufficient to differ C. marlenae sp. nov. from C. sarasinorum or C. schenkeli but it might be confused with reddish specimens of C. longidigita. Caridina marlenae sp. nov. is showing large bright white dots on reddish colouration of the entire body. In C. sarasinorum, the body is coloured dark brown with faint light transversal bands on first, third, fifth and sixth abdominal segments (W. Klotz, pers. observation on the comparative material listed above). In C. schenkeli the colouration of the body is mostly transparent with some brownish or whitish blotches.
In preserved condition, C. marlenae sp. nov. can be distinguished from C. sarasinorum by the more reduced epipods (slightly reduced on the third maxilliped, absent from all pereiopods vs. well developed (with distal hooks) on the third maxilliped and first pereiopod in C. sarasinorum and the slender chelipeds and pereiopods (in detail: chela of first pereiopod 3.00–3.83 times as long as wide vs. 1.74–2.1 times in C. sarasinorum, 1.00–1.05 times as long as carpus vs. 1.35–1.48 times in C. sarasinorum, dactylus 1.88–2.50 times as long as palm vs. 0.83–1.05 times as long in C. sarasinorum, carpus 3.85–4.77 times as long as wide vs. 1.75–2.22 times in C. sarasinorum, merus 3.80–4.25 times as long as wide vs. 1.78–2.63 times in C. sarasinorum. Chela of second pereiopod 3.69–4.38 times as long as wide vs. 2.19–2.64 times in C. sarasinorum, dactylus 1.80–2.25 times as long as palm vs. 1.05–1.33 times as long in C. sarasinorum, carpus 6.78–9.80 times as long as wide vs. 4.56–5.05 times in C. sarasinorum, merus 5.33–6.50 times as long as wide vs. 3.60–4.29 times in C. sarasinorum. Dactylus of third pereiopod 4.40–5.33 times as long as wide vs. 4.0–4.20 in C. sarasinorum, propodus 13.67–16.25 times as long as wide vs. 10.00–11.11 in C. sarasinorum, 3.56–4.06 times as long as dactylus vs. 2.86–3.13 times as long as dactylus in C. sarasinorum. Propodus of fifth pereiopod 13.43–16.00 times as long as wide vs. 10.00–12.00 in C. sarasinorum).
Caridina marlenae sp. nov. can be distinguished from C. schenkeli by the more reduced epipods (slightly reduced on the third maxilliped, absent from all pereiopods vs. well developed (with distal hooks) on the third maxilliped and first and second pereiopod in C. schenkeli and the slender chelipeds and armature of the dactyli of pereiopods (in detail: chela of first pereiopod 3.00–3.83 times as long as wide vs. 1.90–3.2 times in C. schenkeli, dactylus 1.88–2.50 times as long as palm vs. 1.0–1.4 times as long in C. schenkeli. Carpus of first cheliped 3.85–4.77 times as long as wide vs. 2.1–3.2 times as long as wide in C. schenkeli. Dactylus of second pereiopod 1.80–2.25 times as long as palm vs. 1.2–1.4 times as long in C. schenkeli, carpus 6.78–9.80 times as long as wide vs. 4.5–6.5 times in C. schenkeli. Dactylus of third pereiopod with four or five spiniform setae on flexor margin vs. with 6–8 spiniform setae in C. schenkeli. Dactylus of fifth pereiopod with 24–31 serrate setae on flexor margin vs. with 57–64 in C. schenkeli.
Caridina marlenae sp. nov. can also be distinguished from C. longidigita by the type of chelae built for scraping vs. for filter-feeding in C. longidigita (brushes of setae short on tips of fingers of chelipeds vs. setae long, chela of first cheliped 3.00–3.83 times as long as wide vs. 4.6–6.5 times as long as wide in C. longidigita, dactylus 1.88–2.50 times as long as palm vs. 3.6–4.6 times as long in C. longidigita, carpus 3.85–4.77 times as long as wide vs. 4.8–8.1 times in C. longidigita; chela of second pereiopod 3.69–4.38 times as long as wide vs. 4.8–6.4 times in C. longidigita, dactylus 1.80–2.25 times as long as palm vs. 3.4–3.9 times as long in C. longidigita).
Holotype
: ov. ♀ cl. 3.0 mm (
Cephalothorax and cephalic appendages. Postorbital carapace length 1.3–3.8 mm (n = 220). Rostrum (Fig.
Caridina mayamareenae sp. nov. Morphology 1. Paratype ♂, cl. 2.7 mm,
Abdominal somites, telson and uropods. Sixth abdominal somite 0.46–0.71 (median 0.58, n = 8) times carapace length, 1.65–2.0 (median 1.74, n = 8) times as long as fifth somite, 0.90–1.12 (median 1.04, n = 8) times as long as telson. Telson (Fig.
Mouthparts and branchiae. Incisor process of mandible (Fig.
Caridina mayamareenae sp. nov. Morphology 2. Paratype ♂, cl. 2.7 mm,
Pereiopods. Chelae of first and second pereiopods (Fig.
Pleopods. Endopod of male first pleopod (Fig.
Body colouration of large females whitish, frequently with broad bright red stripes and blotches, eggs green (Fig.
Ovigerous females with few eggs (36, n = 1). Size of undeveloped eggs (early stage embryos without eyespot) 0.71–0.78 × 0.39–0.54 mm, size of developed eggs (late stage embryos with eyes) 0.78 × 0.47 mm (n = 9).
Named after the fourth author's, daughter for her strong interest in decapod crustaceans her father is working on.
Caridina mayamareenae sp. nov. is endemic to Lake Poso. Specimens were found at five localities within the lake, three in the northern part and two at the eastern and western shores in the southern part of the lake.
Caridina mayamareenae sp. nov. is hiding inside empty shells of the viviparid snail Celetaia persculpta (P. Sarasin and F. Sarasin, 1898) and Tylomelania spp. (Fig.
Abundance of Caridina mayamareenae sp. nov. in shells of aquatic snails in Lake Poso. The numbers in brackets in the “shells” column refer to numbers of shells of Celetaia persculpta / shells of Tylomelania spp.; in the “other taxa” column, the numbers are juvenile gecarcinucid crabs / n Cirolana spp.
Locality and depth | shells (n) | shrimps (n) | Other taxa |
---|---|---|---|
E shore: | |||
Dolidi Ndano, 15m | 28* | 66 | -# |
W shore: | |||
Bay N of Cape Bancea, 15m | 22 (13/9) | 13 | 6/2 |
NW shore: | |||
Cape Wotu | |||
10m | 25 (16/9) | 30 | -/1 |
15m | 27 (27/0) | 35 | 4/8 |
Siuri, 13–14m | 19 (4/15) | 23 | 4/- |
Among all species of the genus Caridina known from Lake Poso, C. mayamareenae sp. nov. is unique by its short and conspicuous high rostrum, the less developed chelipeds with scarce setae at the tip of the fingers, and the strong third pair of pereiopods. A high and rather short rostrum is an infrequent character among lacustrine species of the genus Caridina from the Central Lakes of Sulawesi (compare revision in
Holotype
: ov. ♂ cl. 2.7 mm (
Other material
: 1 ♂ cl. 2.7 mm (
Cephalothorax and cephalic appendages.
Postorbital carapace length 2.6–3.8 mm (n = 36). Rostrum (Fig.
Caridina poso sp. nov. Morphology 1. ♂, cl. 2.7 mm,
Abdominal somites, telson and uropods.
Sixth abdominal somite 0.60–0.76 (median 0.67, n = 12) times carapace length, 1.70–2.18 (median 1.95, n = 11) times as long as fifth somite, 0.93–1.11 (median 1.08, n = 9) times as long as telson. Telson (Fig.
Mouthparts and branchiae.
Incisor process of mandible (Fig.
Pereiopods. Chelae of first and second pereiopods (Fig.
Caridina poso sp. nov. Morphology 2. Paratype ♂, cl. 2.7 mm,
Pleopods. Endopod of male first pleopod (Fig.
Body and legs mottled with reddish and white dots arranged in rows, exopod of uropods with a black and white blotch, antennae dark red, chelae white with red fingers (Fig.
Ovigerous females with few, large eggs (5 and 9, n = 2). Size of eggs 0.96–1.11 × 0.56–0.66 mm (n = 9).
The specific name is a noun in apposition after the type locality, Lake Poso.
Caridina poso sp. nov. is endemic to Lake Poso. Specimens were found at three localities within the lake, one at the east shore and two at the west shore.
Caridina poso sp. nov. lives in packs of debris (small to medium-sized stones) close to the shore of the Lake Poso and thus could be considered a hard substrate dweller as defined in
With its long and upturned rostrum, C. poso sp. nov. is similar to C. ensifera and C. caerulea, two endemic species to Lake Poso. In the field, colouration alone is sufficient to differenciate C. poso sp. nov. from these species. The much smaller species C. poso sp. nov. (carapace length 2.6–3.8 mm) is showing black and white blotches on the exopod of the uropods. In the larger species C. ensifera (cl. 3.5–5.3 mm), a dark red spot is seen on the exopod of the uropods. In C. caerulea (cl. 3.0–4.5 mm), the exopod of the uropods shows an elongate blue blotch (
In preserved condition, C. poso sp. nov. can be distinguished from C. ensifera by the absence of epipods on all pereiopods (a vestigial epipod is present on third maxilliped vs. epipods well developed, with distal hooks on the third maxilliped and first and second pereiopods in C. ensifera) and by the higher number of postorbital teeth on the rostrum (3–5 (mode 4) vs. 1–3 (mode 2) in C. ensifera). Further, C. poso sp. nov. differs by its slender chelipeds (chela of first pereiopod 3.1–3.4 times as long as high vs. 2.0–2.8 times in C. ensifera, dactylus of first cheliped 2.0–2.5 times as long as palm vs. 1.0–1.3 times in C. ensifera, dactylus of second cheliped 1.5–2.3 times as long as palm vs. 1.2–1.4 times in C. ensifera) and slender third pair of pereiopods (propodus 16.5–19.1 times as long as wide vs. 10–13 times in C. ensifera, carpus 8.7–10.4 times as long as wide vs. 4.7–6.1 times in C. ensifera, merus 11.3–13.9 times as long as wide vs. 9.2–11.4 times in C. ensifera). In contrast, the dactyli of the fifth pereiopods are shorter (dactylus 2.4–4.7 times as long as wide vs. 5.4–7.0 times in C. ensifera, propodus 4.4–5.3 times as long as dactylus vs. 2.5–3.0 times in C. ensifera). The dactyli of fifth pereiopods are armed with a smaller number of serrate setae on the flexor margin (30–34 vs. 51–57 in C. ensifera). Caridina poso sp. nov. differs from C. caerulea by the absence of epipods on all pereiopods (a vestigial epipod is present on the third maxilliped) vs. epipods well developed (with distal hooks) on the third maxilliped and first and second pereiopods and the higher number of postorbital teeth on the rostrum (3–5 (mode 4) vs. 2–4 (mode 2)) in C. caerulea; further by its shorter telson (telson 0.6–0.7 times as long as carapace vs. 0.8 times in C. caerulea), by the slender chelipeds (chela of first pereiopod 3.1–3.4 times as long as high vs. 1.9–2.7 times in C. caerulea, dactylus of first cheliped 2.0–2.5 times as long as palm vs. 1.1–1.4 times in C. caerulea, carpus of first cheliped 3.1–4.3 times as long as wide vs. 2.1–2.5 times in C. caerulea; chela of second cheliped 3.2–3.9 times as long as wide vs. 2.1–3.2 times in C. caerulea, dactylus of second cheliped 1.5–2.3 times as long as palm vs. 1.3–1.6 times in C. caerulea, carpus of second cheliped 6.5–8.4 times as long as wide vs. 4.1–5.4 times in C. caerulea). The third pair of pereiopods is more slender (propodus 16.5–19.1 times as long as wide vs. 12.9–16.3 times in C. caerulea, carpus 8.7–10.4 times as long as wide vs. 5.9–8.0 times in C. caerulea, merus 11.3–13.9 times as long as wide vs. 9.4–11.8 times in C. caerulea). Merus of fifth pereiopod slender, 11.5–12.9 times as long as wide vs. 8.5–11.3 times in C. caerulea.
We used sequences of mitochondrial DNA to investigate the phylogenetic relationship among the species of Caridina from Lake Poso as described above. The resulting sequence alignments have a length of 781 bp (COI) and 540 bp (16S), respectively. In 16S, only two short and largely unambiguous indels (1–2 bp) were required to homologise positions in the alignment.
If support values are considered, the tree topologies reconstructed from 16S and COI are largely congruent (Suppl. material
The molecular phylogeny of Lake Poso species for this study and from the previous study with fewer species (
Molecular phylogeny of the 11 species of Caridina in Lake Poso. Phylogenetic relationships reconstructed by BI analyses of two mitochondrial gene fragments (topology based on concatenated 16S and COI datasets). Number of branches show, from top, Bayesian posterior probabilities (> 0.85) and ML/MP bootstrap values (> 70). An asterisk indicates nodes with full support (1/100/100). The scale bar indicates the substitution rate. See Suppl. material
The molecular phylogeny and field observations (colour pattern, habitat, distribution, behaviour if applicable) were used to test and support the morphological studies of alcohol preserved specimens. The integrative taxonomic approach taken by
The match of morphospecies and genetic clades remains as heterogeneous as in
The new species cluster within the Poso clade (Fig.
The occurrence of a Lake Poso species in empty snail shells (i.e., Caridina mayamareenae sp. nov.; Fig.
In Lake Tanganyika, East Africa,
So far, Limnocaridina iridinae and the parallel case of C. mayamareenae sp. nov. from Lake Poso are the only cases of freshwater shrimps in general, and particularly in ancient lake species flocks, associated with molluscs. As a possibly morphological adaptation to their habitat, both species share the less developed type of chelae bearing just some scarce setae at the tips of fingers in contrast to the brush-like dense tufts of setae found in other atyids. A similar association was only described for C. spongicola from the Malili lake system, Sulawesi. This species is associated with an endemic freshwater sponge from Lake Towuti and one of the most extreme specialisations found in the adaptive radiation of Caridina in the ancient lakes of Sulawesi (
Following the IUCN categories, all previously described species from Lake Poso and catchment (Table
The key to pre-sorting living specimens in the field can be used easily without having to use microscopic equipment. Shrimps can, for example, be observed while swimming or snorkelling or by putting them in small fish tanks, and releasing back into the water afterwards. The key can be used for pre-sorting in the field for scientific purpose but also for sustainable capacity building or citizen science projects without having to reduce the populations. This key, however, has not fully been tested in the field and would certainly be an ideal test case for a local citizen science or student project.
Even in relatively well studied areas like the ancient lakes of Sulawesi, the biodiversity of freshwater shrimps has largely been underestimated. An integrative taxonomic approach is the key to the discovery of new species and to a better understanding of the evolution of Lake Poso's fauna. This new knowledge can contribute to the prevention of biodiversity and habitat loss.
This study was supported by BMBF (project INDOBIOSYS MfN Berlin, 16GW0111K) with regard to the crustacean fauna of Lake Poso. We thank Robert Schreiber (MfN Berlin) for his support of the molecular work in this study. Björn Stelbrink (currently Basel University) and Jobst Pfaender (Potsdam Natural History Museum) helped in collecting some of the samples studied. We further thank the three daughters involved who supported this study in their own way and hope that the lake's, ecosystem and endemic fauna will still be intact when they have grown up. Thanks to both reviewers, Charles Fransen and Yixiong Cai, for their valuable comments that improved the quality of the manuscript.
Table S1. Sample provenience and accession numbers
Data type: molecular data
Supplementary figures
Data type: multimedia
Explanation note: Figure S1. Phylogenetic relationships reconstructed by BI analyses of two mitochondrial gene fragments (topology based on concatenated 16S and COI datasets). The scale bar indicates the substitution rate. Original Bayesian posterior probabilities of Fig.